<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html{
            width:100%;
            height:1000px;
            background:red;
        }

        /* @media 屏幕设备 and (条件) */
        /* 当前屏幕x  <=  1700px == max-width:1700px */
        @media screen and (max-width:1700px){
            html{
                background:green;
            }
        }

        @media screen and (max-width: 1500px){
            html{
                background: blue;
            }
        }
    </style>
</head>
<body>
    
</body>
</html>